1. Field
The subject invention is in the field of extendable/retractable apparatus such as tent poles, fishing rods and boat hooks which can be set at any length within a length range. More specifically it is in the field of such apparatus which incorporates mechanism by which one mechanism at one end of the apparatus operates and controls another mechanism at the other end of the apparatus. Still more specifically it is in the field of such apparatus and related mechanisms adapted for use with apparatus used in construction of dry walls in buildings, apparatus known in the trade as a flat finishing box, used in the crowning and finishing of taped joints between drywall panels.
2. Prior Art
Known prior art is shown in the patents listed below. These patents are:
2,934,937 4,592,797 3,105,262 5,088,147 3,146,481 5,099,539 3,090,984
In the field of drywall construction and finishing, apparatus termed a flat finishing box is attached to a handle to enable the operator to apply the box to the joints being serviced by the box. To adapt the apparatus to various use situations various lengths of handles are needed to work with, for example, a variety of heights of ceilings and, also, the box must be set in a range of angles with respect to the long axis of the handle. The conventional apparatus comprises a fixed length handle with a lever at one end operable to lock the box pivoted at the other end of the handle at a specific angle to the handle axis. When a variety of lengths of handles is required, it is necessary either to have a number of flat finishing boxes, each attached to a specific length handle or to use fewer boxes than handle lengths required, (usually one box) and interchange the box or boxes from handle to handle in order to have the box on a handle of suitable length. The use of multiple boxes, each with a different length handle attached, is not generally acceptable because of the cost and because the compound used in the boxes sets up, i.e. hardens, so that compound in boxes not fully emptied in use is wasted and removal of the wasted compound is time consuming. The use of fewer boxes than handles is standard practice but changing the boxes from handle to handle is time consuming and tends to be awkward if the box contains the compound referred to in the trade as "mud".
Therefore, for flat finishing drywall joints more efficiently in terms of the interrelated factors of time and cost, there has been a need for a flat finishing tool with an adjustable length handle, particularly one adjustable to specific lengths in a range of lengths.
U.S. Pat. Nos. 5,099,539 (Forrester) and 5,088,147 (MacMillan, the inventor of the subject invention) both show adjustable length handles for flat finishers. Both of these handles have a lever pivoted at one end and a part called a box footplate pivoted at the other. In use a flat finishing box is attached to the footplate, the handle is adjusted to the needed length, and the handle is maneuvered to place the box against the work surface. This placement sets the box and footplate at an angle to the long axis of the handle and the lever is operated to lock the box and footplate at that angle relative to the handle. The mechanical complexity of these prior art adjustable length handles for flat finishers is typical in the prior art increases first and maintenance costs of the handles and degrades their reliability, thereby increasing operation costs. The lock mechanism in particular tends to be delicate relative to its performance requirements and the range of angular motion of the box footplate is quite limited.
Accordingly, the primary objective of the subject invention is to provide a less complicated adjustable length handle for flat finishes because of the significant savings in costs that the reduced complication facilitates. Other objectives are that the range of angular motion of the box footplate be relatively large, that there be no highly loaded small parts, that the handle be relatively lightweight and that it be ergonomically acceptable.